As is known in the automotive industry, there are at present acoustic devices located in the inner part of a vehicle engine's air filter, which can be, for example, the known sound-reducers or truncated-cone sound reducers, made of plastic or metal, which are generally coupled around circular openings (1-A1, 2A1)--see FIG. 1 annexed hereto, showing a lateral cross-section of a type of conventional air filter (10) located and made respectively on one side of the air filter's upper compartment (1) and lower compartment (2), the air filter element (3) remaining pressed between the two compartments (1, 2) and the internal supports for the air filter element (3).
In accordance with FIG. 1, the air is aspirated by the dirty air inlet nozzle (1-A) of the upper compartment (1) and in the aspiration sequence--indicated by trajectory indicated by the larger arrows (S-1)--the air passes through the noise reducer or truncated cone shaped sonorizer, (not shown in FIG. 1), coupled around the circular opening (1-A1). The air then enters the upper compartment (1), then passes through the filtering element (3), enters the lower compartment (2) of the air filter (10) and passes through the noise reducer or truncated cone shaped sonorizer of the lower compartment (2) that is coupled around the circular opening (2-A1), entering the purified air exit nozzle (2-A) and then into the vehicle's engine, whereby, simultaneously and inversely to the trajectory described above and indicated by larger arrows (S-1), there is a sequence of inlet noises by means of sound waves. These sound waves are shown sequentially by bold arrows (S-2), which finally exit through the dirty air inlet nozzle (1-A) of the upper compartment (1) of the air filter (10).
However, these prior art internal noise reducers or truncated cone shaped sonorizers are integral parts usually made of plastic or also metal. These materials are non-acoustical and are rather noise propagators. The reducers or sonorizers allow by reason of their truncated cone shape only a modest dampening of the inlet noises--by breaking up the sound waves--and that include the engine's and air aspiration noises, exiting through the dirty air inlet nozzle (1-A).
The current technology also includes the known external acoustical tubes or boxes that control the engine's air inlet and that are arranged upstream of the air filter--being coupled to the dirty air inlet nozzle (1-A) of the upper compartment (1) of air filter (10); but even with the use of these external, acoustic tubes or boxes, the internal noise reducers or truncated cone shaped sonorizers, by reason of being made of plastic or metal, effectively do not cause the desirable technical effect of noise reduction, because they do not absorb the acoustical waves. It is finally noted that the addition of these prior art tubes or boxes contributes to increase the costs of this technique, in addition to taking up much room in the engine's compartment.